Create a new REST resource in iRODS interface to create/remove project groups

[johren@bbn.com]

• This will be used by the GENI portal to create a project group in iRODS when a new project is created in the GENI Portal.
• The remove functionality is included for completeness but will likely not be used since projects do not currently go away in the GENI Portal (they only go dormant).
• Add gimiadmin to the project group when it is created.
• Gracefully handle if the project already exists on create or doesn't exist on remove.